Glyphosate, or N-phosphonomethylglycine (HOOCCH.sub.2 NHCH.sub.2 PO (OH).sub.2), is a well-known translocated, postemergence, broadspectrum herbicide. The typical commercial formulation contains about 41% of the isopropylamine salt of glyphosate and is believed to contain about 16-20% by weight of a tallow amine ethoxylate surfactant. Glyphosate is a relatively insoluble acid, and thus is typically formulated and applied as a salt, such as the isopropylamine, sodium or ammonium salt.
Surfactants are incorporated into the formulation to improve the activity of the glyphosate. However, the term "surfactant" is ambiguous, as the form supplied by manufacturers is not necessarily a single compound, but can be a mixture. For example, with ethoxylated surfactants, the degree of ethoxylation can be and typically is a statistical mixture. The literature describes use of surfactants in glyphosate compositions and in particular, Weed Science, Vol. 25, pp 275-287 (1977) demonstrates the necessity of including a surfactant in glyphosate formulations. However, tallow amine ethoxylate is a severe eye irritant.
Conventional glyphosate formulations include the use of surfactants such as silicone to enhance the rainfast properties of glyphosate formulations. However, commercialization of such formulations has been hindered by the cost of incorporation of such surfactants into the formulations, and by the hydrolytic instability of such adjuvants. Other formulations including surfactants are disclosed in U.S. Pat. Nos. 5,362,705, 5,180,414 and 5,118,338.
Adjuvants are typically used in formulations to aid the operation or improve the effectiveness of the pesticide, herbicide, or other active ingredient. The term includes wetting agents, spreaders, emulsifiers, dispersing agents, foaming adjuvants, foam suppressants, penetrants, and correctives. For example, adjuvants such as Valent X-77.RTM. Spreader are commonly used to enhance the performance of Fluazifop-P-butyl, another selective herbicide. However, Valent X-77.RTM. Spreader and other ethoxylated nonionic surfactants contain free ethylene oxide which may form 1,4 dioxane, a known carcinogen.
It is therefore an object of the present invention to provide glyphosate adjuvants and formulations which do not suffer from the drawbacks of the prior art.
It is a further object of the present invention to provide herbicide formulations with excellent activity, lower irritancy and lower toxicity than conventional formulations.
It is yet another object of the present invention to provide efficacious glyphosate formulations with relatively low amounts of surfactant compared to conventional formulations.